Basic studies will examine the role of endothelial cells in the production of thrombi, the interaction of vessel wall macromolecular and factor XII, interaction of platelets, tumor cells and endothelium and the role of tissue plasminogen activation in limiting thrombosis. Basic and clinical studies will be concerned with platelet-lipoprotein interaction in thrombogenesis, platelet immune injury, and the role of human and bovine factor V in the thrombotic process. In vitro and animal models will be employed to examine platelet-surface interrelationships which we hope will allow development of surfaces for cardiopulmonary bypass that will be less injurious to platelets. Clinical application to cardiopulmonary bypass and hyperlipoproteinemia of basic insights complete the program. Because of its interdisciplinary and interdepartmental nature the proposed program will not only promote creative interactions among investigators but will supplement existing efforts in thrombosis already underway at the University and the Medical Center.